Hybrid Control Scheme for Photovoltaic Microinverter With Adaptive Inductor

This paper studies the two-stage photovoltaic microinverter. Its prestage is a full-bridge dc-dc converter with an adaptive inductor whose inductance can be regulated by a controlled current source. The aim of the adaptive inductor is to realize current boundary continuous mode (BCM) operation with constant frequency and decrease the current stress of the switches in the prestage converter. The structure and operational principle of the proposed adaptive inductor are introduced. The mathematical model has been established for achieving the proper inductance of the adaptive inductor for BCM operation and for verifying the operational condition of the core. The current stress of switches and power loss of the prestage converter with the adaptive inductor or the fixed inductor are analyzed. A hybrid control strategy, which includes an adaptive inductor regulating controller, discontinuous conduction mode operation, and BCM selection in different power ranges, is proposed according to the derived mathematical model. The experimental results are presented to verify the analysis.